Have you seen Amazon's latest convenience/security feature? It's PayPhrase, a way to express-pay at Amazon and participating third-party retailers without entering credit/debit info again and again. Just pick a personal phrase (one you can remember but one that's not easily guessable) and type it in instead of entering billing address, card numbers, etc.
Amazon already stores customer info, so it's quick and easy to access the details for purchases on its site or on retail sites such as J&R and Patagonia. (Interestingly, I searched "PayPhrase" on several of the participating sites and came up empty. No info on this payment option.)
If PayPhrase catches on, it might challenge PayPal and other competing services. Technology Review mentions security concerns, because people tend to use the same phrases over and over. Still, the same holds true for most passwords. But without more promotion, PayPhrase won't gain the kind of traction it needs to become part of the shopping routine.